No Ethernet! Help!

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Hopefully, one or both of these factoids will save you several hours of Googling and general frustration if attempting similar DIY IT upgrades and the Ethernet connection goes kaput.

Virtual Box Networking Fail

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I recently installed Virtual Box on both my Windows 7 laptop and my MacBook Air in order to run Ubuntu as a virtual machine.  I downloaded the latest versions of Virtual Box and Virtual Box extensions, as well as the Ubuntu 13.10 x64 ISO image and completed the relatively painless installation procedure.   After restarting the VM and logging in, I discovered, much to my chagrin, that Ubuntu couldn’t access the Internet.   The easy solution:

Log in to Ubuntu and open a terminal.
$ cd /etc/network
$ sudo gedit interfaces (enter your password when prompted)

Add the following 2 lines to the interfaces files:

auto eth0
iface eth0 inet dhcp

Save the file.

$ sudo ifdown eth0
$ sudo ifup eth0

Problem solved!

Apple AirPort Time Capsule Meets Comcast Cable Modem.  MAC address Mayhem Ensues.

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Yesterday, I decided to upgrade my ancient WiFi router.   Thinking I could kill two birds with one stone, I bought an Apple Airport Time Capsule and picked it up on the way home from work at the local Apple Store.   Way back in prehistory, my laptop at the time had been directly connected to the cable modem.  Comcast associates a single MAC address with the cable modem (for no particularly good reason other than to charge customers more to rent a cable modem with an integrated router).   I own my cable modem.  When I subsequently added the aforementioned WiFi router, I got around connection problems by spoofing the MAC address of the laptop using the Netgear router configuration web app.   Pretty much all routers known to man have this feature.   Except, of course, Apple AirPort routers.   Apple earns well-deserved accolades for industrial design, but sometimes these industry-standard, yet mysteriously lacking features made me shake my fists and fume with rage.  What gives Apple?!?

Thankfully, the solution in this case is relatively low-tech, but does involve some patience:  1) Unplug the cable modem.  2) Unplug the AirPort Time Capsule.  3) Disconnect the coaxial cable from the cable modem.  4) Disconnect everything except the WAN Ethernet cable from the AirPort.  5) Wait 15-30 minutes.  Yes, suffer in silence without broadband Internet for a half an hour.   6) Reconnect the coaxial cable to the cable modem.  7) Connect the AirPort WAN Ethernet cable to the cable modem.  8) Power on the AirPort FIRST.  9) Power on the cable modem.  10) Wait until all of the link lights on the cable modem are blinking, probably green or blue.  11) Attach a Mac to the AirPort using an Ethernet cable.   12)  Open the AirPort Utility on the Mac and click on the AirPort Icon.    Release the DHCP address.   13) Wait a few seconds to allow the cable modem to identify and fully grok the Ethernet WAN MAC address of the AirPort.  14)  Pat yourself on the back when the Internet works.